Laminar-flow airfoil

Abstract

An upper wing surface of a laminar-flow airfoil for decreasing an undesirable head-lowering pitching moment around an aerodynamic center of the airfoil. The upper wing surface includes: a convex front profile portion extending from a leading edge to a largest-thickness point located corresponding to 38% of a wing chord length. A convex central profile portion extends from the largest-thickness point to a position corresponding to 90% of the wing chord length at which a value obtained by dividing a thicknesswise difference between the position and the largest-thickness point by a distance in a direction of the wing chord from the largest-thickness point is equal to or smaller than 0.12. A concave rear profile portion extends from a position corresponding to 95% of the wing chord length to the trailing edge. The rear profile portion forms a pressure gradient is steeper than that formed by the central profile portion.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]The present nonprovisional application claims priority under 35 USC 119 to Japanese Patent Application No. 2002-0170786 filed on Jun. 12, 2002 the entire contents thereof is hereby incorporated by reference.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to a novel trailing edge shape of a laminar-flow airfoil, in which a head-lowering pitching moment around an aerodynamic center, which is a problem peculiar to a laminar-flow airfoil, is suppressed.[0004]2. Description of the Related Art[0005]A boundary layer on a surface of a main wing of an airplane is a laminar-flow boundary layer at a leading edge, but changes from the laminar-flow boundary layer to a turbulent-flow boundary layer toward a trailing edge. A friction drag on the surface of the main wing is smaller at the laminar-flow boundary layer than at the turbulent-flow boundary layer. For this reason, in order to decrease the drag on t...

AI Technical Summary

Benefits of technology

[0013]Accordingly, it is an object of the present invention to decrease an undesirable head-lower

Problems solved by technology

However, when a portion of a wing surface in the vicinity of a leading edge is rough, the largest lift disadvantageously tends to decrease largely, leading to a great problem during takeoff or landing of the airplane.

These laminar-flow airfoils enables a reduction in the drag, but have a problem of causing a large head-lowering pitching moment.

Moreover, because these laminar-flow airfoils are for use in a low-speed range, they have a problem of causing drag-divergence phenomenon at an early stage, of a subsonic speed range.

However, the largest lift in a lower Reynolds number range is small and the capacity of an inner-wing fuel tank is insufficient because the wing thi

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